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Piston switcher

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Piston switcher

Unread postAuthor: igpay » Sun Jun 22, 2008 12:40 pm

Some of you may remember that I wanted to build a shotgun not so long ago. Well, this little device will allow you to combine two modded sprinkler valve pneumatics to make a shotgun of sorts, or a Halo-esque rocket launcher, or anything that has two barrels that alternate firing.
This design uses a piston to alternate which valve uses the blowgun to exhaust the air on top of the diaphragm. When the first gun is filled up with air, it comes out of the hose on top of the first gun's valve, and pushes the piston to block the second valve's hose. Then the second gun is filled up, but the air coming out of this valve's hose is blocked by the piston. When the blowgun is pulled the first time, only the air from the first valve is let out, triggering that valve only. But when the blowgun is pulled the second time, a spring has pushed back the piston to let the air from the second valve out. There would be some sort of mechanism restraining the piston from going too far in either direction, so technically the spring doesn't even have to be there, we could rely solely on air pressure. I also had a design that uses only one valve, but I forgot it at the moment, so I'll post it later.
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Attachments
pistonswitcher.jpg
This is the piston switcher in first position, where it will activate the first valve. The blue stuff is the air pressure.
pistonswitcher2.jpg
This is the piston switcher after valve 1 has fired. Now valve 2 is ready to fire. The blue stuff is the air pressure.
Last edited by igpay on Mon Jun 23, 2008 11:45 am, edited 1 time in total.
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Unread postAuthor: SpudFarm » Sun Jun 22, 2008 1:02 pm

i really don't understand your diagrams
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Unread postAuthor: igpay » Sun Jun 22, 2008 1:02 pm

spudfarm wrote:i really don't understand your diagrams

Sorry about that, what don't you understand? maybe I can help you.
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Unread postAuthor: SpudFarm » Sun Jun 22, 2008 1:06 pm

what is the point? there is no seat :S
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Unread postAuthor: igpay » Sun Jun 22, 2008 1:26 pm

Aggh! I'm a noob. Whats a seat? :oops:
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Unread postAuthor: Launch-Tek » Sun Jun 22, 2008 1:59 pm

If I'm not missing something, I think the piston would oscillate at the outlet too rapidly and not dump either quickly.
It would be cool for me to be proved wrong on this because it would have a lot of potential if it works.
Maybe with a longer heavy piston it would better.
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Unread postAuthor: MrCrowley » Sun Jun 22, 2008 2:07 pm

I too have no idea what's going on. It looks like you are using Macromedia flash to draw it, try MS Paint.
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Unread postAuthor: Copperboy » Sun Jun 22, 2008 2:26 pm

I understand the idea, and it's really clever! Though the diagrams may be a bit wrong (it could be designed so that spring constant would be of no significance) the concept's good. There's some flaws, and a dangerous one could be that when nr.1 has fired and the piston moves, nr.2 may experience a sudden drop in pressure, which may cause it to fire.
Build a prototype! :P
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Unread postAuthor: Maniac » Sun Jun 22, 2008 4:44 pm

I think I understand what you are trying to do but it will probably not work.
So you are trying to make the piston switch back and forth between barrels. Where is your air resiviour. And when that first piston fires all of the air will probably be dumped.
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Unread postAuthor: igpay » Mon Jun 23, 2008 11:44 am

MrCrowley wrote:I too have no idea what's going on. It looks like you are using Macromedia flash to draw it, try MS Paint.

I'm on A mac, so I used Photoshop Cs 2. I have windows on the mac, but I was in a hurry to make these images, so I didn't reboot in windows.

I think Copperboy is the only one who really understands this concept, so let me try to explain. If I'm correct, a modded sprinkler valve works by having a diaphragm with equal air pressure above and below it. Usually, the sprinkler valve is just fired by having a blowgun that releases the air from above the diaphragm. In this design though, the air from above the diaphragm would be directed into a chamber with a piston. The air pressure from one of the valves would hold the piston forward, blocking the outlet for the air above the diaphragm in the other valve. Once the blowgun is triggered, the air from above the diaphragm in the first valve would be released, and the piston would be allowed to slide back. Now the air from above the diaphragm in the second valve would fill the chamber, allowing that air to be released via blowgun. This whole assembly would have to be incredibly small in order for the valves not to accidentally fire. I do plan on making this, but only once I build up some funds.
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Unread postAuthor: psycix » Mon Jun 23, 2008 2:19 pm

So this mechanism is to pilot two guns with two clicks on the same trigger?
Note that if you hold it a lil bit too long, both guns will pilot, and if you want to pilot only one of em, you cant pilot very effectively.

Also, O-rings are a must.
Id rather prefer using a 3-way ballvalve for more safety, reliability and control.
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Unread postAuthor: TwitchTheAussie » Mon Jun 23, 2008 4:48 pm

I understand whats going on here. With the piston your sealing off either side of the barrels, so that only one side gets the pressure. I dont think the piston is a good idea. Maybe a hammer style valve would work better? You dont really need all the fiddly bits of a piston.
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Unread postAuthor: Copperboy » Tue Jun 24, 2008 3:49 am

Like psycix say, it's important to add some kind of "delay mechanism" in order not to pilot both of them simultaneously... hmm... now it's getting complex (at least to construct). It would be so sweet though, a side by side shotgun..
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